Annals of Neurology; Published Online: November 14, 2011 (DOI:10.1002/ana.XXX).

Sponsors: This research was supported by NINDS Grants RO1-NS40467 and U10-NS31321, the Michael J. Fox Foundation, Parkinson’s Unity Walk, The Valley Foundation, and James and Sharron Clark.

What we found

Risk of Parkinson's disease was increased 6-fold in people who worked with the solvent TCE (trichloroethylene) and 10-fold in those who worked with PERC (perchloroethylene; tetrachloroethylene)

Exposure preceded Parkinson's disease onset by 30-40 years

How was the study done

We studied 99 pairs of twins in which 1 twin had Parkinson's disease and the other twin didn’t

We asked them detailed questions about their jobs and hobbies, focusing on job tasks and materials

Experts estimated lifelong exposure to 6 common solvents

Exposures were compared in the twins with and without Parkinson's disease

Why this matters

All of us are exposed to TCE and PERC in the environment

In industry, TCE is used to remove grease from metals and other materials

PERC is the leading solvent used in dry-cleaning, and is also used as a degreaser and spot remover

People who don’t “work” with TCE have been exposed through its use in dozens of common household products such as spot removers, glues, carpet cleaners and paints.

Both TCE and PERC persist in the environment. TCE is the most common organic contaminant in groundwater.

Millions of pounds of both solvents are released into the environment each year

Next steps

Like all epidemiology studies, our results need to be replicated before we can be certain that TCE and PERC cause Parkinson's disease

In our study, exposure preceded Parkinson's disease onset by several decades, suggesting that if we understand the toxic mechanism we can potentially intervene to prevent Parkinson's disease

Additional studies in the laboratory could help to explain the toxic effects of TCE and PERC on the brain, hopefully leading to preventive therapies

Additional Information

There have been a few “case reports” of Parkinson's disease occurring in people who worked with TCE, but this is the first analytic epidemiology study to link TCE or PERC exposure with Parkinson's disease

Ref: Gash et al, Ann Neurol 2008;63:184–192

Animal studies also support a biological link between TCE and Parkinson's disease

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